The webcam portion of most usb cameras should work out of the box with most linux distributions. You can see if it's detected and a driver loaded by looking for the presence of a video0 node: ls /dev/video0

The sound portion can be trickier, depending on your audio setup. On a system using only alsa, the mic is likely seen as a different sound device. You may need to configure you desktop sound system to take mic input from the webcam device inside of an audio in jack found on the built-in sound card. Under KDE, kmix allows this and it works well. Gnome or other desktop environments should have an equivalent tool for their sound systems as well.